This invention relates to an extruded metal tube, having internal, longitudinally extending, spline-like ribs, and a method for forming the tube, which may be used as a drive shaft for connecting a driving device to a driven device. The tube is formed of a thin wall extrusion with the opposite ends of the wall thickened for forming connecting means for connecting the tube to other devices.
Large drive shafts, such as those which are commonly used for trucks and other heavy duty automotive vehicles are formed out of elongated tubes. A connection means is formed on each of the opposite ends of the tubes. For example, a splined connection portion may be welded on one end of the tube and a lug connection may be welded on the opposite end of the tube. In this example, the spline may connect with a power output of an engine transmission while the lug may connect to the power input of a differential which transmits the power, through axles, to the drive wheels of the vehicle. These large drive shafts are subject to considerable torsion or torque loads during portions of their rotation under different speed and power transmission loads and, thus, their walls must be thick enough to resist whipping or flexing or twisting during
Thus, the invention herein is concerned with reducing the thickness of the walls of drive shafts, to reduce their costs, while simultaneously strengthening the shafts and reducing shaft deformation resulting from rotation.
Extruding metal tubes of the general type involved here, is known. For example, my prior U.S. Pat. Nos. 4,277,969 issued July 14, 1981 for a Method for Cold Forming Tubes with Interior Thicker Wall Sections, and No. 4,292,831 issued Oct. 6, 1981 for a Process for Extruding a Metal Tube with Inwardly Thickened End Portions, disclose tubes and processes for extruding such tubes. Other prior patents issued to me generally disclose processes for forming metal tubes with thickened portions. Examples are my prior U.S. Pat. No. 3,837,205 issued Sept. 24, 1974 and No. 3,886,649 issued June 3, 1975, and other such similar patents. Thus, this present application is concerned with an improvement which particularly adapts a cold formed or cold extruded tube for use as an improved, heavy duty power transmission drive shaft and for other purposes.